Method and apparatus for performing a channel availability query for a plurality of locations

ABSTRACT

The present invention relates to a method and apparatus for channel availability query on multiple locations in a wireless local area network system. A method for a station (STA) to perform a channel query procedure in a wireless communication system comprises: transmitting, at a first STA corresponding to a channel availability query requesting STA, a first message to a second STA supporting the channel availability query procedure, wherein the second STA corresponds to a channel availability query responding STA, wherein the first message comprises device location information of one or more locations for the channel availability query; and receiving, at the first STA from the second STA, a second message comprising channel availability information, wherein the channel availability information is commonly applicable to multiple locations within an area, when the device location information of the first message is for the multiple location within the area.

This is a U.S. National Phase Entry of PCT Application No.PCT/KR2011/007829, filed Oct. 20, 2011, and claims the benefit of U.S.Provisional Application No. 61/453,558 filed Mar. 17, 2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for channelavailability query on multiple locations in a wireless local areanetwork (WLAN).

2. Discussion of the Related Art

Standards for wireless local area network (WLAN) technologies have beendeveloped as IEEE 802.11 standards. IEEE 802.11a provides a transmissionrate of 54 Mbps and IEEE 802.11b provides a transmission rate of 11 Mbpsusing an unlicensed band at 2.4 GHz or 5 GHz. IEEE 802.11g provides atransmission rate of 54 Mbps using orthogonal frequency-divisionmultiplexing (OFDM) at 2.4 GHz. IEEE 802.11n provides a transmissionrate of 300 Mbps for 4 spatial streams using Multiple Input MultipleOutput OFDM (MIMO-OFDM). IEEE 802.11n supports channel bandwidths of upto 40 MHz and, in this case, provides a transmission rate of 600 Mbps.

IEEE 802.11af standards for regulating WLAN operation of an unlicenseddevice in a TV whitespace zone is under development.

TV whitespace includes VHF bands (54 to 60 MHz, 76 to 88 MHz, and 174 to216 MHz) and UHF bands (470 to 698 MHz) which are assigned to broadcastTV. The TV whitespace means a frequency band allowed to be used by anunlicensed device on the condition that the unlicensed device does notdisturb communication of licensed devices (TV broadcast, wirelessmicrophone, etc.) operating in the frequency band.

While all unlicensed devices are permitted to operate in frequency bandsof 512 to 608 MHz and 614 to 698 MHz except some special cases,frequency bands of 54 to 60 MHz, 76 to 88 MHz, 174 to 216 MHz and 470 to512 MHz are allowed only for communication between fixed devices. Afixed device means a device that transmits signals only at a fixedlocation. In the following description, a whitespace band includes theaforementioned TV whitespace. However, the whitespace is not limitedthereto.

An unlicensed device that wants to use a whitespace band needs toprovide a protection function for licensed devices. Accordingly, theunlicensed device must check whether the licensed devices occupy thewhitespace band before starting transmission in the whitespace band.

To achieve this, the unlicensed device needs to access a geo-locationdatabase through the Internet or a dedicated network to acquireinformation on a list of channels available in the corresponding area.The geo-location database stores and manages information on licenseddevices registered therein and channel usage information that isdynamically changed according to geo-locations and used time of thelicensed devices.

A station (STA) can execute a spectrum sensing mechanism. An energydetection scheme, a feature detection scheme, etc. can be used as thespectrum sensing mechanism. For example, it is possible to determinethat a channel is being used by a licensed device or an incumbent userwhen the intensity of a received signal exceeds a predetermined value ora DTV preamble is detected. When it is determined that a channeladjacent to a currently used channel is used by an incumbent user, anSTA and an AP need to decrease transmit power.

SUMMARY OF THE INVENTION

As described above, an STA needs to acquire information on availablechannels in a whitespace band to operate in the whitespace band. Thepresent invention proposes a method and apparatus for an STA that wantsto perform a WLAN operation in a white space band to efficiently executea channel availability query. Particularly, the present inventionprovides a method for performing a channel availability query onmultiple locations rather than updating available channel informationwhen an STA moves, and a signal format therefor.

According to an aspect of the present invention, a method for a station(STA) to perform a channel availability query procedure in a wirelesscommunication system includes: transmitting, at a first STAcorresponding to a channel availability query requesting STA, a firstmessage to a second STA supporting the channel availability queryprocedure, wherein the second STA corresponds to a channel availabilityquery responding STA, wherein the first message comprises devicelocation information of one or more locations for the channelavailability query; and receiving, at the first STA from the second STA,a second message comprising channel availability information, whereinthe channel availability information is commonly applicable to multiplelocations within an area, when the device location information of thefirst message is for the multiple location within the area.

The channel availability information may be obtained from a registeredlocation server, and the second STA may be a registered location server.

The device location information may include geo-location positioninformation with at least latitude, longitude and radius information,and the radius information may indicate a radius in a horizontal planefrom a point designated by the latitude and longitude information.

The first message may further include information indicating a number ofthe device location information.

The device location information about the one or more locations may beof one or both of first and second types, the first type may be definedon the basis of geo-location position information with at leastlatitude, longitude and radius information, and the second type may bedefined on the basis of a plurality of device location information.

The channel availability information may be applicable to a firstlocation among the multiple locations, when there is no channelavailability information commonly applicable to the multiple locationsand the device location information of the first message is for themultiple locations within the area.

The channel availability query procedure may be performed by using ageneric advertisement service (GAS) protocol, and the first STA and thesecond STA may employ a registered location query protocol (RLQP).

In this case, the first message may further include a reason result codeindicating the first message is for a channel availability query requestand STA identity information for the addresses of the channelavailability query requesting STA and the channel availability queryresponding STA.

The second message may further include a reason result code indicating afirst value or a second value, wherein the first value indicates thechannel availability information is commonly applicable to the multiplelocations within the area, and the second value indicates the channelavailability information is for a first location among the multiplelocations.

According another aspect of the present invention, a station deviceoperable as a first station (STA) of a channel query procedure in awireless communication system includes: a transceiver supporting thechannel query procedure, and configured to transmit a first messagecomprising device location information of one or more locations forchannel availability query to a second STA supporting the channel queryprocedure and corresponding to a channel availability responding STA ofthe channel query procedure, and to receive a second message includingchannel availability information from the second STA; and a processorconnected to the transceiver and configured to control the transceiverto operate the first STA as a channel availability query requesting STAof the channel query procedure, wherein when the device locationinformation is commonly applicable to multiple locations within an area,when the device location information of the first message is for themultiple locations within the area.

According another aspect of the present invention, a method for astation (STA) to perform a channel query procedure in a wirelesscommunication system includes: receiving, from a first STA correspondingto a channel availability query requesting STA, a first message at asecond STA supporting the channel query procedure, wherein the secondSTA corresponds to a channel availability query responding STA, whereinthe first message comprises device location information of one or morelocations for the channel availability query; and transmitting, to thefirst STA by the second STA, a second message comprising channelavailability information, wherein the channel availability informationis commonly applicable to multiple locations within an area, when thedevice location information of the first message is for the multiplelocations within the area.

According another aspect of the present invention, a station deviceoperable as a second station (STA) of a channel query procedure in awireless communication system includes: a transceiver configured toreceive a first message comprising device location information of one ormore locations for a channel availability query from a first STAcorresponding to a channel availability query requesting STA of thechannel query procedure, and to transmit a second message comprisingchannel availability information to the first STA; and a processorconnected to the transceiver and configured to control the stationdevice to support the channel query procedure and operate as a channelavailability query responding STA of the channel query procedure,wherein the channel availability information is commonly applicable tomultiple locations within an area, when the device location informationof the first message is for the multiple locations within the area.

Advantageous Effects

According to the above-mentioned embodiments of the present invention,an STA that wants to perform a WLAN operation in a whitespace band canefficiently perform a channel availability query procedure.Particularly, even when the STA moves, the STA can perform a channelavailability query on multiple locations rather than updating availablechannel information when it moves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary WSM information element;

FIG. 2 illustrates a channel map field included in the WSM shown in FIG.1;

FIG. 3 illustrates an exemplary registered location field for describingthe present invention;

FIG. 4 illustrates a campus environment for describing an exemplaryembodiment of the present invention;

FIG. 5 illustrates a whitespace zone formed within a predeterminedradius with a specific point as the center according to an exemplaryembodiment of the present invention;

FIG. 6 is a view referred to for describing restrictions on the use of aWSM in the whitespace zone according to an exemplary embodiment of thepresent invention;

FIG. 7 is a view referred to for describing an operation of a dependentAP to request an enabling STA to provide WSM information according to anexemplary embodiment of the present invention;

FIG. 8 is a view referred to for describing a scheme of defining awhitespace zone according to an exemplary embodiment of the presentinvention;

FIG. 9 illustrates a channel availability query procedure;

FIG. 10 shows a channel availability query frame format according to anexemplary embodiment of the present invention;

FIG. 11 shows a channel query information field format according to anexemplary embodiment of the present invention;

FIG. 12 shows exemplary device location information according to anexemplary embodiment of the present invention;

FIG. 13 shows device location information about a personal/portabledevice; and

FIG. 14 is a block diagram illustrating a configuration of an STAcapable of implementing the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention with reference to the accompanying drawings. Thedetailed description, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present invention, rather than to show the only embodiments that canbe implemented according to the invention. The following detaileddescription includes specific details in order to provide a thoroughunderstanding of the present invention. However, it will be apparent tothose skilled in the art that the present invention may be practicedwithout such specific details.

In some instances, known structures and devices are omitted or are shownin block diagram form, focusing on important features of the structuresand devices, so as not to obscure the concept of the invention. The samereference numbers will be used throughout this specification to refer tothe same or like parts.

As described above, an STA that wants to operate in a whitespace bandneeds to acquire information on an available channel in the whitespaceband. The information on an available channel may have a WSM (WhiteSpace Map) format.

FIG. 1 illustrates an exemplary WSM information element.

A WSM information element is used for a specific STA (e.g., an enablingSTA or a dependent AP that enables a dependent STA) to signal a channelavailable for transmission to other STAs (e.g., dependent STAs). The WSMinformation element can be transmitted being included in a managementaction frame such as a beacon frame, a probe response frame, a WSMannouncement frame, etc.

A WSM in a TV whitespace band includes information indicating whether aTV signal occupies a channel. The WSM can indicate the numbers ofchannels available for unlicensed devices at a specific time and maximumallowable power values in the available channels in the form of a list.

An enabling STA can transmit a WSM to a dependent STA. A dependent APenabled by the enabling STA transmits a WSM to a dependent STA. The WSMcan be used to efficiently support scanning procedures of dependent STAsoperable in a whitespace band, as described above. That is, thedependent STA can scan only a specified WLAN channel only in anavailable channel designated by the received WSM.

In the WSM information element shown in FIG. 1, a country code fieldprovides information on the location of a channel map following thisfield. With respect to TV whitespace, countries may have different TVbands and TV channel bandwidths, and different regulatory domains areassigned to the countries. Accordingly, the country code field helpsrecognize the physical location of a TV channel available for an STAthat receives the WSM along with a channel map field.

The country code field can be signaled as a country string value of 3octets. That is, the first 2 octets may indicate a country code definedin ISO/IEC 3166-1 and the last octet may mean an environment. Thecountry code field can include more detailed information than countryinformation in an extensive manner. For example, the country code fieldcan include a regional code value of a specific country.

Although the basic unit of a channel map that signals whether or not achannel is available is not limited to a TV channel bandwidth, the basicunit can be channel information in the smallest basic unit provided by adatabase of a corresponding regulatory domain.

The channel map field includes an available channel number (e.g., TVchannel number) and a maximum transmit power level corresponding to eachavailable channel (TV channel) according to FCC regulations. FIG. 2illustrates the channel map field of the WSM information element shownin FIG. 1.

As shown in FIG. 2, the channel map field of the WSM can include adevice type field. An enabling STA or a dependent AP that transmitschannel map information preferably signals a device type correspondingto a device to be provided with a service from the enabling STA ordependent AP along with a channel map when transmitting the channel mapbecause an available channel and a maximum allowable transmit powerlevel may depend on device type. For example, a fixed device cannot usea channel adjacent to a TV channel being used by an incumbent user.Conversely, a personal/portable device can use a channel next to a TVchannel being used by an incumbent user on the condition that a maximumallowable power level in the channel is reduced from 100 mW to 40 mW.

Therefore, the channel map preferably includes the device type fieldwith an available channel number (e.g. TV channel number) and a maximumtransmit power level corresponding to each available channel accordingto FCC regulations. The device type field signals the type of a device,which is provided with the service from the enabling STA or dependent APand can use the WSM, rather than signaling the type of a device thattransmits the WSM.

Specifically, the device type field can signal a spectrum mask value ofan STA that can use the WSM with information on a fixed device and apersonal/portable device.

A fixed device may not be allowed to use a WSM having a device typecorresponding to a personal/portable device. This is because a channelunavailable for the fixed device may be signaled as an available channelwhen the device type field of the WSM is set to a personal/portabledevice.

The channel map shown in FIG. 2 includes a registered location field.The registered location field is geo-location information represented asa three-dimensional coordinate (latitude, longitude, altitude). Theregistered location field may include latitude, longitude and altitudevalues and their resolutions. The registered location field may furtherinclude information indicating whether the corresponding locationinformation corresponds to an enabling STA or a dependent STA.

FIG. 3 illustrates an exemplary registered location field.

The format shown in FIG. 3 is based on the DSE registered locationelement body field defined in IEEE 802.11y standard. A dependentenablement identifier, a regulatory class, and a channel number includedin the registered location field can be set to reserved values.

The above-mentioned WSM information element can signal an availablechannel list at a specific location indicated by the locationinformation in the format as shown in FIG. 3. However, if an STA thathas received the WSM moves from the location by a predetermined range ormore, the STA needs to receive the WSM again and make a channelavailability query again to receive the WSM. To solve this problem,according to an aspect of the present invention, there is provided amethod of querying available channel information of multiple locationsand receiving a WSM according to the available channel informationquery.

For example, an enabling STA can acquire information about channelsavailable in not only the location thereof but also multiple locationsaround the location. The enabling STA can combine available channelinformation acquired in this manner to set a geographical area havingthe same available channel. This geographical area has a boundarydefined as a specific cooperate set. Even when an STA moves in thegeographical area, the available channel is valid so long as the STA iswithin the boundary, and thus it is not necessary to update theavailable channel. A geographical area based on a plurality of locations(points) will be referred to as a whitespace zone hereinafter.

A dependent STA can start to operate by receiving an enable signal froman enabling STA. At this time, it is possible to consider a case inwhich a plurality of dependent STAs enabled by a specific enabling STAis located in a specific geographical range.

FIG. 4 illustrates a campus environment for describing an exemplaryembodiment of the present invention.

Referring to FIG. 4, an enabling STA is present and a plurality ofdependent STAs enabled by the enabling STAs is distributed in thecampus. The dependent STAs can move to different buildings, differentlecture rooms, and different floors in the campus. In a regionallydivided service environment, such as the campus or an office/apartment,it is more efficient to use common channel information available in thedivided regions. Particularly, it is expected that the common availablechannel information is useful in a rural area because an availablechannel is hardly changed according to location in the rural area.

The whitespace zone range can be represented in various forms. Forexample, the whitespace zone can be represented as an area within apredetermined radius with the geo-location coordinate point of aregistered location as the center. Although the whitespace zone can haveany form, the physical location of the whitespace zone needs to becalculated in association with registered location information.

For example, a location can be registered as a three-dimensionalcoordinate of (x1, y1, z1) and a whitespace range can be set as a radiusvalue. In this case, a spherical whitespace zone having a radius with(x1, y1, z1) as the center of the sphere can be set.

When an altitude value of registered location information about apersonal/portable device is omitted, a whitespace zone can be specifiedas an area within a predetermined radius from a point designated bylatitude and longitude values of the registered location information ina plane.

As described above, a common available channel can be used in a specificzone in a campus/rural area. However, the common available channel isnot limited to the campus or rural area, and it is possible to calculateand use a common channel valid for all STAs located in one whitespacezone as necessary.

A method of operating a WSM according to an exemplary embodiment of thepresent invention will now be described with reference to FIG. 4.

In FIG. 4, the dependent STAs located in the specific range start tooperate by being enabled by the enabling STA. Here, the enabling STAtransmits an enable signal and a WSM. The WSM may have the format shownin FIG. 1 and available channel information may have the channel mapshown in FIG. 2. The dependent STAs receiving the WSM from the enablingSTA can communicate on the basis of an available TV channel number and amaximum transmit power level signaled through the channel map.

The enabling STA according to the current embodiment acquires a channelcommonly available in a whitespace zone range, set by the enabling STA,through information on channels available in multiple locations andtransmits information on the common available channel. This can beachieved by performing an AND operation on sets of channels available inmultiple locations to calculate the intersection of the channel sets.

While no restriction is imposed on a method used for procedures ofderiving optimized location information and available channelinformation required for the calculation, a common available channel,finally computed in a location selected from a whitespace zone range,needs to be applied to the method.

The enabling STA can set a whitespace zone first, and then selectmultiple locations that can cover the whitespace zone by computing them.Alternatively, the enabling STA can calculate an appropriate whitespacezone from locations of dependent STAs previously registered in theenabling STA and provided with the service from the enabling STA, orspecific location information. The order of the whitespace zone andlocation may depend on the algorithm of deriving them.

FIG. 5 illustrates a whitespace zone formed within a predeterminedradius having a specific point as the center according to an exemplaryembodiment of the present invention.

A boundary as shown in FIG. 5 can be set by a whitespace zone designatedby an enabling STA. Locating in the whitespace zone means presence ofthe corresponding coordinate within the boundary of the whitespace zone.The enabling STA can acquire information on channels available inmultiple locations from a database or a registered location server(RLS), calculate a channel commonly available in the whitespace zone,and signal the common available channel to dependent STAs located in thewhitespace zone. The enabling STA can signal the common availablechannel through an enable signal and WSM, as described above.

A registered location field of the WSM corresponds to geo-locationinformation of the enabling STA and a whitespace zone range of the WSMis represented in the form of a radius from the registered location or alocation vector. A dependent STA that has received the WSM can calculatethe whitespace zone indicated by a dotted line in FIG. 5 by combiningthe two fields of registered location field and whitespace zone range.

FIG. 6 is a view referred to for describing restrictions on the use of aWSM in a whitespace zone according to an embodiment of the presentinvention.

A dependent STA can operate using the same available channel whilefreely moving in the calculated whitespace zone. However, if thedependent STA moves out of the whitespace zone set by the enabling STA,channel map information acquired from the enabling STA is not valid anymore. Accordingly, the channel map information needs to be updated forthe dependent STA when the dependent STA moves out of the whitespacezone.

The channel map information is updated according to circumstances. In acase that the dependent STA can maintain its enabled state whilecontinuously communicating with the enabling STA although it has movedout of the whitespace zone, the dependent STA can request a new WSM inorder to acquire the WSM. If the enabling STA provides only thewhitespace zone, the dependent STA is de-enabled when moving out of thewhitespace zone, and newly enabled by another enabling STA.

A dependent STA can operate as illustrated in FIG. 6 without registeringgeo-location information thereof. However, a dependent STA that wants tooperate as a master device, such as an AP (Access Point), needs toregister geo-location information thereof in a location server or adatabase through the enabling STA.

A dependent STA is able to register location information thereof, toquery channels available at the coordinate corresponding to the locationinformation, to receive information on a list of channels available atthe coordinate in the form of a WSM, and to use the channel list.

In this case, the registered location and whitespace zone range in thechannel map shown in FIG. 2 can have null values. However, when thedependent STA moves by a predetermined distance (e.g., 100 m) or longerfrom the registered coordinate, the available channel list is not validany more.

The dependent STA may want to set a whitespace zone and move in thewhitespace zone while using the same channel. In this case, thedependent STA transmits a WSM request frame to the enabling STA.

FIG. 7 illustrates an operation of a dependent AP to request an enablingSTA to provide WSM information according to an exemplary embodiment ofthe present invention.

Upon receipt of a WSM request frame, the enabling STA can transmit a WSMresponse frame including a channel map having the format as shown inFIG. 2 in response to the WSM request frame. Here, a registered locationfield of the WSM response frame corresponds to geo-location of thedependent AP (STA). A whitespace zone range of the WSM response framemay correspond to a radius from the registered location or a locationvector indicating multiple locations.

While the registered location is assumed to be the location of theenabling STA in FIGS. 5 and 6, it is assumed that location informationregistered when the moving dependent STA requests the WSM is used as theregistered location in FIG. 7.

The enabling STA can acquire information on channels available inmultiple locations in the whitespace zone on the basis of registeredgeo-location information of the dependent STA and information onlocations around the location of the dependent STA by requesting adatabase to provide the available channel information, and calculate acommon available channel. This is achieved by performing an ANDoperation on sets of channels available in the multiple locations tocalculate the intersection of the channel sets.

While no restriction is imposed on a method used for procedures ofderiving optimized location information and available channelinformation required for the calculation, a common available channel,finally computed at a location selected from a whitespace zone range,needs to be applied to the method.

The dependent STA can operate using the same available channel whilefreely moving in the calculated whitespace zone. Accordingly, thedependent STA needs not newly acquire information about an availablechannel whenever the geo-location thereof is changed by a predetermineddistance (e.g., 100 m) or more when the dependent STA operates whilemoving.

However, when the dependent STA moves out of the whitespace zone set bythe enabling STA, channel map information acquired from the enabling STAis not valid any more. Accordingly, the WSM needs to be updated.

The WSM request frame may include registered location and radiusinformation. In this case, the dependent STA sets the whitespace zone,and the enabling STA calculates the whitespace zone on the basis of theregistered location and radius information upon receipt of the WSMrequest frame. The enabling STA can select appropriate or most suitablemultiple locations included in the calculated whitespace zone andacquire information on channels available in the locations from adatabase (or registered location server). Similarly to the scenariosillustrated in FIGS. 5 and 6, the enabling STA can compute a commonavailable channel from the acquired available channel information. Theenabling STA can configure a channel map with the information on thecommon channel available in the calculated whitespace zone, include thechannel map in a WSM of a WSM response frame, and transmit the WSMresponse frame to the dependent STA.

While the aforementioned embodiments of the present invention havedescribed the scheme of setting a whitespace zone, which is operatedusing a common WSM, on the basis of a radius having a specific pointdesignated by latitude and longitude as the center (first type) and thescheme of designating the whitespace zone based on a location vectorindicating information on multiple locations, it is also possible toconfigure the whitespace zone using both the two types.

FIG. 8 is a view referred to for describing a scheme for designating awhitespace zone according to an embodiment of the present invention.

As described above, zone information for handling a WSM which iscommonly applicable to multiple locations can be configured usingspecific point p1 designated based on latitude/longitude and radius r1in a plane from the specific point p1, or using multiple points p1 andp2. Furthermore, these two schemes can be simultaneously applied in anexemplary embodiment of the present invention. For example, in FIG. 8,ranges within specific radiuses r1 and r2 from the points p1 and p2 canbe used as location information for configuring a whitespace zone.

A description will be made of a method of acquiring available channelinformation based on multiple locations when an STA performs channelavailability query (CAQ) in order to obtain an available channel list.

As described above, the STA must consider protection of an incumbentuser to operate in a whitespace band. Accordingly, the STA needs toaccess a whitespace band database or a location server to registerlocation information thereof and acquire a list of available channels. Aprocedure of acquiring an available channel list is called a CAQprocedure.

FIG. 9 illustrates an exemplary CAQ procedure.

A CAQ procedure employing a registered location query protocol (RLQP)uses a registered location secure server (RLSS) or an RLS in order toregister an available channel list. Here, although the RLSS or RLS donot have to transmit/receive WLAN signals, the RLSS or RLS is afunctional entity connected with an STA (e.g. STA 2 of FIG. 9) thatadvertises RLQP through a wired or wireless connection means. STA 2 maybe regarded as the same entity as the RLSS or RLS.

Referring to FIG. 9, STA 1 can receive an advertisement protocol elementindicating that STA 2 supports RLQP in step S1210. That is, STA 1 canreceive a management frame having an advertisement protocol IDcorresponding to RLQP from STA 2.

STA 1 that wants to operate in a whitespace band can transmit a CAQrequest message as a CAQ requesting STA to STA 2 (S1220). FIG. 10 showsa channel availability query frame format according to an embodiment ofthe present invention.

Referring to FIG. 10, a CAQ action field can include a device class,device identity information, device location information, and a WSM.Particularly, the device location information field can be repeatedaccording to the present embodiment. Accordingly, an STA can signalmultiple locations in one frame by repeating device locationinformation. In this case, it is necessary to indicate that thecorresponding query relates to the multiple locations. An exemplarychannel query information field format for indicating the query aboutthe multiple locations is shown in FIG. 11.

FIG. 11 shows a channel query information field format according to anexemplary embodiment of the present invention. In the case of CAQ formultiple locations, a device location information present field is setto 1 so as to indicate presence of location information. A fieldindicating the quantity of device location information represents thenumber of locations relating to the corresponding query.

FIG. 12 shows exemplary device location information according to anembodiment of the present invention.

Referring to FIG. 12, device location information includes vicinityinformation in addition to latitude, longitude and altitude information.The vicinity information may be another expression of the radiusdescribed in the above embodiment. In addition, the device locationinformation includes a vicinity present field that represents thepresence of the vicinity information. 32 bits following the vicinitypresent field indicates vicinity information.

If the vicinity present field indicates 0 (off), the device locationinformation indicates a query about the corresponding specific locationpoint. For example, when vicinity corresponds to a radius, a whitespacezone with a radius of 1 Km can be designated for one point. However, itis also possible to set a whitespace zone based on a query about aplurality of point locations at a resolution distance (50 m) or less.

In an exemplary embodiment of the present invention, when there is aplurality of pieces of device location information, the device locationinformation may not include vicinity information (or radiusinformation). Because it can be considered that a zone corresponding toa resolution distance is set at each point when a plurality of points isdesignated, it is unnecessary to designate additional vicinityinformation (radius information).

FIG. 13 shows device location information regarding a personal/portabledevice. The device location information may not include an altitudevalue, as described above. In this case, vicinity information can bedesignated in a plane defined by latitude and longitude values. Table 1shows exemplary device location information presented in TLV form.

TABLE 1 Name Type Length Value Range Device <ANY> 18 The device locationAF_CAQ, Location information contains the US Infor- latitude, longitude,and mation altitude information of the device with the format using thefirst 128 bits of DSE registered location element in 8.4.2.54, in whichthe last 5 bits (B123? B127) remains reserved. It is set from thedot11STALCITable MIB object. When the device type subfield of the deviceclass field (Table E-af2) is not set to fixed TVBD, B80-B119 of DSEregistered location element in 8.4.2.54 is set to vicinity information.

Referring back to FIG. 9, upon receipt of the CAQ request message, STA 2can transmit the CAQ request message to the RLSS or RLS. When thedatabase/RLS receives a query about multiple locations, the database/RLScalculates a channel commonly available in a whitespace zone determinedbased on combination of the multiple locations (corresponding torespective areas) and transmits a CAQ frame in response to the CAQrequest message. The CAQ frame is transmitted to STA 1 via STA 2 (S1240and S1250). If STA 2 corresponds to the RLSS or RLS, the RLSS or RLSresponds to the query of STA 1 about the multiple locations (S1240 andS1250 are omitted).

As described above, when one or more channels commonly available inmultiple locations are present, a WSM including information on thechannels commonly available in the multiple locations can be received asa CAQ response message. According to an embodiment of the presentinvention, however, an available channel list corresponding to the firstlocation of multiple locations is provided while a CAQ response messageprovides no information when one or more channels commonly available inthe multiple locations are present. In this case, it is impossible tosecure a list of channels commonly available in a whitespace zone toeliminate the necessity of updating WSM whenever an STA moves. However,available channel information corresponding to the current location ofan STA that requests CAQ can be provided such that the STA can performWLAN operation at the current location thereof first.

To discriminate a CAQ request and a CAQ response from each other, anembodiment of the present invention proposes a cause effect code asfollows.

TABLE 2 Reason result code Description 0 Reserved 1 Channel AvailabilityList requested 2 Reserved 3 Success with the available channel listresult 4 Request declined 5 Request not successful because of device IDverification failure 6 Request not successful as one or more parametershave invalid values 7 Handshake timeout 8 Success with the availablechannel list result for WSZ 9-255 Reserved

That is, in an embodiment of the present invention, when CAQ request isperformed as illustrated in FIG. 9, it is possible to indicate that acorresponding frame corresponds to a CAQ request message using reasonresult code 1. Reason result code 8 indicates that a CAQ responsemessage includes information on a channel commonly available in a zoneformed based on multiple locations for the CAQ request. Reason resultcode 3 represents that a common available channel is not provided butavailable channel information corresponding to the first location ofmultiple locations is provided.

FIG. 14 is a block diagram illustrating a configuration of an STAcapable of implementing the present invention.

Referring to FIG. 14, an STA device 100 may include a processor 101, amemory 102, an RF (Radio Frequency) unit 103, a display unit 104, and auser interface unit 105. Functions of layers including a physicalinterface protocol layer can be executed by the processor 101.

The memory 102 is electrically connected to the processor 101 and storesan operating system, applications and general files.

If the STA device 100 is a user device, the display unit 104 can beimplemented using known LCD (Liquid Crystal Display), OLED (OrganicLight Emitting Diode), etc. and display various information. The userinterface unit 105 can be configured in such a manner that it iscombined with a known user interface such as keypad, touch-screen, etc.

The RF unit 103 is electrically/functionally connected to the processor101 and transmits/receives RF signals. The RF unit 103 can include atransmission module and a reception module. The RF unit 103 may bereferred to as a transceiver.

The transmission module can code and modulate signals and/or data thatare scheduled by the processor 101 to be transmitted, and then deliverthe signals and/or data to an antenna.

The reception module can decode and demodulate an RF signal receivedthrough the antenna to restore the RF signal to original data andtransmit the original data to the processor 101.

The transceiver of the STA 100 can support a channel query procedure,transmit a first message including device location information of one ormore locations for CAQ to a peer STA corresponding to a channelavailability query responding STA of the channel query procedure, andreceive a second message including channel availability informationacquired from an RLS or RLSS from the peer STA.

The processor 101 can be configured to regard channel availabilityinformation to be commonly available in multiple locations in a specificzone when the device location information included in the first messagecorresponds to information on the multiple locations in the specificzone.

The detailed description of the preferred embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the preferred embodiments, those skilled in the artwill appreciate that various modifications and variations can be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. For example, an embodimentof the present invention may be constructed by combining components orconfigurations of the above-described embodiments of the presentinvention. Accordingly, the invention should not be limited to thespecific embodiments described herein, but should be accorded thebroadest scope consistent with the principles and novel featuresdisclosed herein.

Industrial Applicability

While the embodiments of the present invention have been described basedon IEEE 802.11, the embodiments can be equally applied to various mobilecommunication systems in which an unlicensed device can perform channelavailability query in a whitespace band.

What is claimed is:
 1. A method for a station (STA) to perform a channelavailability query procedure in a wireless communication system, themethod comprising: transmitting, at a first STA corresponding to achannel availability query requesting STA, a first message to a secondSTA supporting the channel availability query process, the second STAcorresponding to a channel availability query responding STA, the firstmessage comprising device location information of one or more locationsfor the channel availability query; and receiving, at the first STA fromthe second STA, a second message comprising channel availabilityinformation, wherein, when the device location information of the firstmessage is for multiple locations within an area and the second messageindicates that the channel availability information is commonlyapplicable to the multiple locations, the channel availabilityinformation is commonly applicable to the multiple locations within thearea, and wherein, when the device location information of the firstmessage is for the multiple locations within the area and there is nochannel availability information commonly applicable to the multiplelocations, the channel availability information is applicable to a firstlocation among the multiple locations.
 2. The method according to claim1, wherein the channel availability information is obtained from aregistered location server.
 3. The method according to claim 1, whereinthe second STA comprises a registered location server.
 4. The methodaccording to claim 1, wherein: the device location information comprisesgeo-location position information comprising at least latitude,longitude, and radius information; and the radius information indicatesa radius in a horizontal plane from a point designated by the latitudeand longitude information.
 5. The method according to claim 1, whereinthe first message further comprises information indicating a number ofthe device location information.
 6. The method according to claim 1,wherein: the device location information about the one or more locationsis of one or both of first and second types; the first type is definedbased on geographical point information comprising at least latitude,longitude, and radius information; and the second type is defined basedon a plurality of device location information.
 7. The method accordingto claim 1, wherein: the channel query process is performed by using aGAS protocol; and the first STA and the second STA employ a RLQP(Registered Location Query Protocol).
 8. The method according to claim7, wherein the first message further comprises: a reason result codeindicating that the first message is for a channel availability queryrequest; and a STA identity information for the addresses of the channelquery requesting STA and the channel query responding STA.
 9. The methodaccording to claim 7, wherein: the second message further comprises areason result code indicating a first value or a second value; the firstvalue indicates that the channel availability information is commonlyapplicable to the multiple locations within the area; and the secondvalue indicates that the channel availability information is for a firstlocation among the multiple locations.
 10. A station device operable asa first station (STA) of a channel query procedure in a wirelesscommunication system, the station device comprising: a transceiversupporting the channel query procedure, and configured to: transmit afirst message comprising device location information of one or morelocations for the channel availability query to a second STA supportingthe channel query procedure and corresponding to a channel availabilityresponding STA of the channel query procedure; and receive a secondmessage including channel availability information from the second STA;and a processor connected to the transceiver and configured to controlthe transceiver to operate the first STA as a channel availability queryrequesting STA of the channel query procedure, wherein, when the devicelocation information of the first message is for multiple locationswithin an area and the second message indicates that the channelavailability information is commonly applicable to the multiplelocations, the channel availability information is commonly applicableto the multiple locations within the area, and wherein, when the devicelocation information of the first message is for the multiple locationswithin the area and there is no channel availability informationcommonly applicable to the multiple locations, the channel availabilityinformation is applicable to the first location among the multiplelocations.
 11. A method for a station (STA) to perform a channel queryprocedure in a wireless communication system, the method comprising:receiving, from a first STA corresponding to a channel availabilityquery requesting STA, a first message at a second STA supporting thechannel availability query process, the second STA corresponding to achannel availability query responding STA, the first message comprisingdevice location information of one or more locations for the channelavailability query; and transmitting, to the first STA by the secondSTA, a second message comprising channel availability information,wherein, when the device location information of the first message isfor multiple locations within an area and the second message indicatesthat the channel availability information is commonly applicable to themultiple locations, the channel availability information is commonlyapplicable to the multiple locations within the area, and wherein, whenthe device location information of the first message is for the multiplelocations within an area and there is no channel availabilityinformation commonly applicable to the multiple locations, the channelavailability information is applicable to a first location among themultiple locations.
 12. A station device operable as a second station(STA) of a channel query procedure in a wireless communication system,the station device comprising: a transceiver configured to: receive afirst message comprising device location information of one or morelocations for a channel availability query from a first STAcorresponding to a channel availability query requesting STA of thechannel query procedure and transmit a second message comprising channelavailability information to the first STA; and a processor connected tothe transceiver, and configured to control the station device to supportthe channel query procedure and operate as a channel availabilityresponding STA of the channel query procedure, wherein, when the devicelocation information of the first message is for multiple locationswithin an area and the channel availability information is commonlyapplicable to multiple locations, the channel availability informationis commonly applicable to the multiple locations within the area, andwherein, when the device location information of the first message isfor the multiple locations within the area and there is no channelavailability information commonly applicable to the multiple locations,the channel availability information is applicable to a first locationamong the multiple locations.
 13. The method according to claim 1,wherein, when the device location information of the first message isfor the multiple locations within the area and there is no channelavailability information commonly applicable to the multiple locations,the channel availability information is applicable only to the firstlocation among the multiple locations.
 14. The method according to claim1, wherein, when the device location information of the first message isfor the multiple locations within the area and there is no channelavailability information applicable to any of the multiple locations,the second message indicates that the second STA refuses to provide thechannel availability information.